dbragg

iTrader: (7)

i am having an issue with the engine in my SA. i have an MSD box on trailing and on leading. whenever i floor it it makes a loud popping noise and looses power. it seems like it could be detonation, but whenever i shut the car off it backfires. a sign on being rich. i am running a dellorto 48 with a carter pump and holley FPR. i have tried adjusting the fuel up and down, no change. my timing is dead on. the only way i can make the noise go away is to disable the trailing spark. which isnt a HIGE deal, but id prefer to have it and a working tach.

with that being said, i have known this engine for a few years. it came from a doctor who bought the car new. after he bought a corvette in the 90s he parked it in the woods. when i was in HS his son, m age, wanted to drive it. he got it started and then sold it to a friend of mine. my friend had me drive it for him at the drag strip. after the first run whenever i hit a certain rpm it would make the noise and loose almost all power. then it was sold to my neighbor. he wrecked the car and put the engine in his car.

also, this has happened with TWO different carb set ups and two different distributors. so i have no idea what it could be.

i have my MD boxes wired into my 2nd gen fuse block. i have seperate fuses for each box. so i simply pull a fuse to disable the trailing ignition. with the engine running and using only leading when i put in the fuse for the trailing a sound starts coming from somewhere. i have no idea where. then if i floor it it makes this pinging noise. it KIND OF sounds like its coming from the carb.

im STUMPED. any ideas?

ill try to get a video of the noise soon.

djessence

Is it definetly from the carb side of the engine?

Could it be your trailing cables are "leaking" spark, like its jumping? I had thought that made a popping sound and could be directly related to trailing.

Just a thought, im sure someone will correct me

Vashner

So is this a 31 year old block that's survived drag racing, wreak and more?

Vashner

Edit add: BTW The manual saying poping noise could be main bearings.

broke7

iTrader: (1)

check your internal timing. not just your dist timing. I had a similar problem with mine when I put my engine together. The first gen crank pulley can be put on in any postion it doesn't have a offset hole like the 2nd gen. When I first put the new motor in my car it was 90 degrees out (if i remember right) ran great, started great, but popped under power and high rpm. Switched dist,coils, carbs, drove with my lm1 to see if it was lean, and almost pulled the motor. Then before I pulled the motor I put a rb pulley on and compared it to my old pulley and there was the problem. I removed the stock pulley with the hub and found it 90 degrees off compared to the key way compared to the rb one. Needless to say I felt like a dumb ***. So you may want to check that. This can be a common problem normally its 180 out and the car won't run the should be some threads on how to check this that will explain it better than I can

Rx-7Doctor

iTrader: (13)

When this engine was in another car was it also running the MSD boxes?

Sounds like the trailing plugs are firing at the same time.

bad 83

iTrader: (3)

I was thinking the same thing. Or the leading and trailing is backwards.

rxtasy3

iTrader: (2)

is this sitting still and revving or while driving? if while driving, then yes i agree. it could be detonation, but i'd actually have to hear it to say for sure. i've heard detonation before so i know what it sounds like. nothing like in a pist-on. make sure trailing and leading r right, and if so, retard the timing alittle. i thought msd was only used on leading?

Re-Speed.com

iTrader: (3)

He must be sleeping

I have not heard it yet but we have spoken about it.

The MSD was not used when the engine was in the other car. The sound was also present in this chassis without the MSD. He has tried multiple distributors with the same noise present.



-billy

Vashner

In the 85 service manual section 1 it says for engine noise could be;
Knocking noise = carbon buildup.
Hitting noise = malfuction of main or rotor bearing excessive end play, foreign matter in internal gear or stationary gear, or malfunction.

Kentetsu

Sounds like (for whatever reason) the trailing spark is firing at the wrong time.

On the other hand, when my last motor was failing I starting hearing popping noises when I opened the secondaries. When the trailing was disabled, the sound was not nearly as noticeable. Final diagnosis was a failing apex seal...

dbragg

iTrader: (7)

ill have to get a way for you guys to hear it. at a meet i can show the locals and ill work on getting a video/sound clip on here.

Vashner

What does it sound like again? Anything to compare it against? I.E. sounds like =

dbragg

iTrader: (7)

^^ its hard to explain. kind of like ball bearings bouncing around inside of the engine.

ok, a small update:

i havent had time this weekend to mess with it. i drove it to work today and its driving pretty bad. when i got there i had a lot of interest from the coworkers to check her out. while doing so i noticed the newly added fuel filter in the engine bay before the FPR has a good amount of rust specs in it. before the FPR and filter were installed these were going into my carb. since i have a new filter out back too i think the rust is coming from the metal line.

i think my carb needs a total over haul. i have a lead on someone KIND of close that may be able to help me out. ill find out tomorrow.

that still wouldtn explain my other issue though. she gives symptoms like shes detonating and running lean, but she is always backfiring after shut off and initial start up before warming up.

tomorrow after school ill see if i can find a parking lot to play with her in. ill adjust the carb a little and see how good of a sound clip i can get you guys.

rxtasy3

iTrader: (2)

remembering back when mine did it, pull ur trailing plugs if u haven't already. i pulled mine after too changing distributors out. the ceramic around the electrode was broken and when removing them, they would thread out a few turns then stop. after changing these plugs, the knocking stopped. i'm guessing i was running too far advanced for too long.

Kentetsu

Spark knock in a rotary sounds like marbles in a tin can rattling around. Have you checked the timing?

Knocking can also be a symptom of a failing apex seal. Check my thread for more info on that: https://www.rx7club.com/1st-gen-archive-71/engine-signs-failing-rotary-engine-679328/

Vashner

I would suggest a compression test at this point. Also check the eccentric shaft for play. Have you ever removed the main eccentric bolt?

Sorry I don't think that's it just trying to help with process of elimination on surrounding things or stuff in the manual list.

Check oil with magnet for shavings.

dbragg

iTrader: (7)

for everything i know the eccentric shaft bolt has never been removed. i know the original owner of the engine and all of the owners up till me.

i just did an oil change and i didnt notice anything. i still have the old oil, ill run a magnet through it and see if i find any shavings.

i have to go to the gym and then take a test later tonight. after i go to the gym i want to try to get a video for you guys.

kententsu--- thats EXACTLY what mine sounds like, but i hace checked the timing a million times. i have it dead on on trailing and leading. i think im a tooth off cause i am all the way to one side to get dead on, but that wouldnt cause this. plus i have adjusted it many different ways and it still does it. i have watched your autox video and i can faintly hear what youre car was making, but i dont think its the same. during your in car camera i couldnt hear it at all. thats totally different than what im hearing. my noise is WAY louder.

rxtasy3-- i thought about pulling the plugs and changing them. i plan on picking up a set of better plugs the next time i work. ill probably get a set of FC plugs. i ram them in my first 12a and was pleased. the part of your post that confuses me is where you say that when you removed the plugs they would turn out a little bit then stop. so what does that mean?

i think my other issues is cause she is running rich as hell. she smokes shes running so rich, but ill keep it that way until i get this problem solved. she bogs bad right off of idle, but after a second and in the higher rpms she just screams.

heres another question, i had a puerto rican tell me years ago to ditch the metal cap inside the dizzy. he said he does more bad than good. what due you guys think about this?

also, ill compression test it later on. i would do it today but i need a helping hand to do it correctly. i may try to do it by myself.

rxtasy3

iTrader: (2)

i think the reason they would only thread part way out and stop is maybe because of the ceramic being stuck in that small hole. but this is just a guess. i felt extremely lucky that none of that ceramic was left inside the housings.

Kentetsu

You might want to look over the routing of all the plug/coil wires. Also, make sure that the trailing ignitor is actually firing the trailing, and vice versa. A couple years back I was chasing a timing issue, where I could not get rid of spark knock, only to find out that (somehow) the ignitors had ended up backwards (leading trying to fire trailing, vice versa).

gsl-se addict

iTrader: (3)

- do like Kentetsu said and make sure leading is firing leading, trailing firing trailing. Leading ignitor on front of dizzy, trailing near the alt.

- check wiring from coils, though distributor?, to plugs

- even if the big eshaft bolt has never been removed, the pulley itself can go on 4 different ways You could be 90* off and the trailing is firing into the incoming intake charge (next face). This is even worse with the MSD as it fires mulitple sparks over some rotation of the e-shaft.

It sounds like timing is screwed up (L/T crossed, or T2/T1 crossed, or pulley on wrong). If you were firing into the incoming charge, that would cause a massive loss in power and likely the noise you are hearing.

Are you firing through the distributor? On both leading and trailing?

broke7

iTrader: (1)

told him the same thing. had the same problem with my car. it actually started better when it was 90 degrees out

dbragg

iTrader: (7)

here is the video:

http://videos.streetfire.net/video/s...ary_153761.htm

i have been through the wiring a million times, but ill go over it again.

broke7-- some how i didnt see your first post. from all of my knowledge the front pulley has never been off, but im also not the original owner. i think youre right though. that probably is the issue. ill do some research and try swapping it around and see what i can find. like you said though, it starts fine, runs fine, but pops under load and all. i think thats probably what my issue is.

dbragg

iTrader: (7)

well, i did some work today. after taking the top plate off of the engine i realized i had been had. unless im wrong, my flywheel apears stock. i was told it was a RB lightweight on, but apparently not. oh well.

anyways, when the pully is set to TDC the "flat" spot on the flywheel is pointed at the drivers side of the car. so, if im understanding the thread in the archives correctly, my front pulley is 180* off.

here are pics

gsl-se addict

iTrader: (3)

you need to use the inspection plate by the exhaust for this to work. You could also try Jeff's wire method. Really, you just need to figure about where TDC is.. doesn't have to be exact in order to determine if the front pulley is on wrong.

https://www.rx7club.com/showthread.p...&highlight=tdc